BigBlockMopar said

Don't want to hijack the topic but I'm using the stock '73 A-body disc spindles with a homemade outer bearing collar to make up for the bearing difference in the '73 C-body rotors (11.75"/1.25").
With 2 simple washers behind the bracket the calipers lined up perfectly.
Been daily driving this setup for over 3 years already.

In my case it was a case of making use of what I had on the shelf and see if I could make it work.
It's not a 'lightweight' upgrade and setup ofcourse, and I would def. like to go to aluminium calipers in the future, but that would offset the brakebias unfavorable in my case, so for the time being I'll keep using this.

Nice thing about this setup is the trackwidth remained the same, or perhaps even a tad narrower than the 'stock' A-body discbrake system.

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Kernel Sanders said

I knew I had this around somewhere and it took me a bit to find it...

This may help explain why you cant use the backing plates from a Large Bolt Pattern rear with stock Small bolt pattern axles

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